Rothie,
No I've never had that problem. Usually a male of one genus will squabble a bit with a male of another genus over territory but not females.
Of course one thing to keep in mind is that some breeds of fairy wrasses are thought to cross-breed with similar neighbors in the wild. Solars, Yellowflanked, and Orangebacks are all considered siblings and some of these breeds probably evolved over years of crossbreeding with each other while living in the same waters. Scientists are still not sure about how many variants there are of cyanopleura wrasses. And if the coloration of both genus are similar....especially in a female, then you might get some aggression. But that is highly unlikely in captivity. It's tough enough just trying to get same-genus males and females to breed in captivity.
In an aquaruim devoted just to fairy and flasher wrasses any squabbles that will occur will come due to territory setups in the tank. Size and age also will play a role. Or similar colorations will also cause problems (Example: housing a rhomboid with a pyle's fairy might create some aggression). But not due to breeding. If your getting harems to trying your luck at breeding these fish, I'm sorry to say that you'll be losing a lot of money and space in your tank to females. Fairy and flashers just won't breed in regular captive aquariums.
If your purchasing harems because you want a natural setting for your fish or because you want to keep the male colored-up, then it's worth your time, money, and space in an aquarium.
In a fairy aquarium most of your squabbles are small, short and due to territory or a fight over a morsel of food.